The Roche limit is the minimum distance to which a large satellite
can approach its primary body without being torn apart by tidal
forces. If satellite and primary are of similar composition, the
theoretical limit is about 2 1/2 times the radius of the larger body.
The rings of Saturn lie inside Saturn's Roche limit and may be the
debris of a demolished moon. The limit was first calculated by the
French astronomer douard Roche (1820-83). Artificial satellites are
too small to develop substantial tidal stresses.